Low elastic coefficient bodies, devices embodying them and methods of producing them



July 24, 1951 M. E. FINE 2,561,732 LOW ELASTIC COEFFICIENT BODIES,DEvICEs EMBODYING I THEM AND METHODS OF PRODUCING THEM Filed April 13,1950 A 2o QCAA/WA I0 AMWM- A, so 90 PERCENT I IICKEL I lNl/ENTOR By M.E. FINE Mac A TTORNEV Patented July 24, 1951 LOW ELASTIC COEFFICIENTBODIES, DE-

VICES EMBODYING THEM AND METHODS OF PRODUCING THEM Morris E. Fine,Morristown, N .J assignor to Bell Telephone Laboratories, Incorporated,New York, N. Y., a corporation of New York Application April 13, 1950,Serial No. 155,580

13 Claims.

This invention relates to metal bodies the modulus of elasticity ofwhich varies but little over a wide temperature range, to devices whichfunction through the elastic distortion of such bodies, and to methodsof forming such bodies.

When devices which function through elastic distortion of a. metalmember, such as devices embodying mechanical vibratory elements, such asvibrating reeds, tuning forks, or devices embodying springs for applyingor measuring force, are designed to operate under widely varyingclimatic conditions, and when it is required that the operatingcharacteristics of these devices be essentially constant under these.varying conditions, it is necessary that the member be a body whichexhibits as little change in modulus of elasticity as possible over theentire temperature range to which the device may be subjected. Inorderto provide the temperatures encountered, for instance, in aircraftat high altitudes or in tropical climates, in proximity to otherapparatus which may generate heat, it is ordinarily necessary; in orderto achiev these essentially constant operational characteristics, thatprovision be made for limiting any changes in the modulusof elasticityto small values over the temperature range of -50 C. to 150 C.

It has been known that binary iron-nickel alloys containing in thevicinity of 45 per cent nickel have a temperature coefficient of modulusof elasticity which is zero in the vicinity of room temperature.However, this low temperature coefiicient of elasticity obtains forfully annealed material over only a very small temperature range and is,therefore, of littl value in insuring a small change in modulus ofelasticity over a wide temperature range such as that referred to above.The present invention is based upon the factthat the range over whichthe temperature coefficient of. elasticity remains small in ironnickelalloys (which may contain molybdenum as well as other modifyingingredients) can be broadened by cold reduction of bodies ofthe a1- loysand the. fact that the position on the temperature scale at which theselow values. of co-' efficient occur can be controlled by controlof thecomposition of the alloy, the degree of cold working and the subsequentheat treatment. .Bodies of such alloys, when cold reduced andsubsequently heat treated, can be given a stable averagetemperaturecoefiicient of modulus of elasticity which has a low valueover the temperature range set forth above.

A type of apparatus in which bodies so produced can be utilized isexemplified by vibrating reed selector switches, the construction andoperation of which can be most readily understood by reference to theaccompanying drawing, in which:

Fig. 1 is an elevation in section of a portion of a vibrating reedselector switch; and

Fig. 2 is a triaxial diagram on which is shown the range'of alloysutilized in carrying out the present invention.

The critical elements in the vibrating reed selector switch shown inFig. 1 (which switch is more particularly described and claimed in thecopen'ding application of G. E. Perreault, Serial No. 782,528, filedOctober 28, 1947, which issued as Patent 2,502,339 on March 28, 1950)are the vibrating reeds l and 2. These two reeds are separated at oneend by a metallic spacer 3 and are fastened at that end to a support 4.The two reeds and spacer together make up a tuning fork. The reeds l and2 carry tuning bars 5 and 6, respectively, which extend beyond the edgesof the reeds so that their ends can be bent in order to change thevibrational frequency of the reeds. An electrical contact member I is somounted with respect to the tuning bar 5 on the reed I that it is out ofcontact with the tuning bar while the reed is stationary, but it makesperiodic contact with the tuning bar when the reed is vibrated. Theswitch is provided with two external terminals (not shown) one of whichis electrically connected to the contact member I and'the other of whichis electrically connected through the reed l to the contact bar 5.

A plurality of the assemblies described above (only one being shown) arepositioned side by side within common surrounding magnetic winding 8.The reeds in each selector switch unit are tuned to a frequencydifferent from that of the reeds of the other switch units within themagnetic winding. In the operation of the selector the magnetic windingis fed with an alternating current. When the alternating current isof'the same frequency as the natural frequency of vibration of the reedswithin one of the selector switch units, the resulting alternatingmagnetic field causes the vibration of the reed. The vibration of thereed establishes periodic contact between the reed and the contactmember in that switch. By supplying currents of different frequency tothe magnetic winding any one of the switches may be actuated as desired.

The vibrating reeds of these switches are illustrative of elementsoperating through elastic distortion which can be fabricated accordingto the present invention so that their operating characteristic, in thiscase frequency, does not vary excessively over a wide temperature range.

The substantially isoelastic bodies of the present invention can beformed with a modulus of elasticity which changes not more than fiveparts per thousand over the entire temperature range of -50 C. to 150 C.by using alloys having compositions falling within the quadrangle A, B,C, D on the ternary diagram shown in Fig. 2. This figure represents aternary diagram for the system iron-nickel-molybdenum in which the threecoordinates are weight per cent nickel, weight per cent iron, and weightper cent molybdenum. The quadrangle referred to above is formed bystraight lines joining the points A, B, C and D.

Point A represents a composition of 41.5 per cent nickel and 58.5 percent iron. Point B represents a composition of 37 per cent nickel, 11per cent molybdenum and 52 per cent iron. Point C represents acomposition of 42.5 per cent nickel, 45.5 per cent iron and 12 per centmolybdenum. Point D represents a composition of 44.5 per cent nickel and55.5 per cent iron. All alloys falling within this area can be treatedaccording to the present invention to yield the results set forth above.

Preferably, alloys containing at least 2 per cent molybdenum are used.This preferable range of compositions containing at least 2 per centmolybdenum is defined by the area EBCF on the diagram of Fig. 2. Thepoint E on this diagram represents a composition of essentially 41 percent nickel, 2 per cent molybdenum and 5'7 per cent iron. The point Frepresents a composition of essentially 44 per cent nickel, 2 per centmolybdenum and 54 per cent iron.

Particularly for the application to the vibrating reed selector switchesdescribed above, the preferable range of alloy compositions lies between38.5 per cent nickel and 43 per cent nickel, and between 4.5 per centmolybdenum and 9.5 per cent molybdenum, the remainder being iron. Aneven more desirable range lies between 40.5 per cent nickel and 43 percent nickel and between 4.5 per cent molybdenum and 8 per centmolybdenum, the remainder being iron. This latter range of compositionsis shown as the dotted quadrangle on the diagram of Fig. 2. An alloywell suited for use as a vibrating reed in a selector of the typedescribed above contains 43 per cent nickel, 5 per cent molybdenum andthe remainder iron.

To the basic iron-nickel or iron-nickel-molybdenum alloys referred toabove may be added certain modifying ingredients which alter the otherproperties of the alloy but do not have a substantial effect upon themodulus of elasticity. Thus, up to 2 per cent manganese may be added toimprove the working properties of the alloy. Up to .25 per cent carbon,up to 6 per cent aluminum and up to 5 per cent silicon may be present inthe alloys and serve to harden them as well as having minor effects oncertain other properties. Incidental impurities which have no eiTectupon the modulus of elasticity may also be present, though in totalamount less than 2 per cent and preferably less than 1 per cent.

The alloys referred to above are given the advantageous properties ofthe present invention by first subjecting them to a cold workingoperation, such as swaging, rolling, drawing or the like, which reducestheir cross-sectional area and then subjecting them to a low temperatureanneal at a temperature substantially above any temperature to which thebodies may be expected to be exposed during their normal operation. Thearea reduction induced by cold working should be at least 3 per cent andpreferably at least 5 per cent in order to have the required effect uponthe alloy. The upper limit to the amount of cold reduction is set onlyby the amount to which the alloy can be subjected without fracture. Thiscold working results potentially in the required broadening of the lowtemperature coefficient of modulus of elasticity of the alloys referredto above over the broad temperature range referred to above.

However, in this cold worked state the modulus of elasticity will bealtered by a change in the crystalline condition of the alloy as thetemperature is raised above that at which the cold working took place.In order to stabilize the alloy against such a change in modulus it isnecessary to anneal it at a temperature above that to which the alloywill be subjected during its normal oper ation but below the temperaturefor full recrystallization of the alloy. Therefore, with an operatingrange of 50 C. to C. as set forth above, it is necessary that the coldworked body be annealed at at least 150 C. Ordinarily this annealingwill take place in the range of 200 C, to 750 C. or preferably in therange of 300 C. to 60 C. A convenient annealing temperature which yieldsgood results is 400 C. The annealing time is not critical, it beingnecessary only that all parts of the body he allowed to reach theannealing temperature. A convenient annealing time is from one hour tofive hours.

Treatment within the range of conditions as set forth above, whenapplied to the range of alloys described above, results in bodies havinga modulus of elasticity which varies by not more than .5 per cent overthe range of 50 C. to 150 C. By a selection of alloy compositions andconditions of treatment within this range considerably smaller changesin modulus can be achieved.

If modulus of elasticity for any of these bodies is plotted againsttemperature, there occurs somewhere over the temperature scale a pointin the curve at which the value of modulus is a minimum, which pointcorresponds to a zero temperature coefficient of modulus of elasticity.In order to secure the smallest change in modulus over the temperaturerange of -50 C. to 150 C., it is necessary to make the curve in thevicinity of this minimum as shallow as possible and to cause the minimumto fall somewhere near the center of the temperature range.

As may be inferred from the statements above, the curve is made shallowby the operation of cold reduction. The alloys containing molybdenum arealso somewhat more shallow than those which do not. The position of theminimum modulus on the temperature scale can be shifted by varying thecomposition of the alloy (within the ranges set forth above), by varyingthe degree of cold reduction, and by varying the annealing temperature.

In general, the point of minimum modulus on the temperature scale isshifted to a higher temperature with decreasing nickel content and withincreasing molybdenum content in the alloy. The point of minimum modulusis also moved to a higher temperature by increasing the degree of coldreduction and by increasing the annealing temperature. By varying thesefactors one against the other, it is possible to bring the point 01 minum modulus to that point on the temp'eraturescalewhich results in 'avery 'lowover a'll changein modulus over the entire temperature range;I, g

The following four typical examplesillustra'te the low variation inmodulus which can be achieved by the application of these principles, Abinary alloy containing 42.7 percent'nickel, 0.66'fper.cent manganeseand the remainder iron was subjected to a cold area reduction of 78 percent and was then annealedat400Cl 'I he resultingabodyhad a modulus ofelasticity which changed by only .1 per cent over therange from 50 C.,to150 C. 1

Similarly, a ternary alloy of 42.1 percent nickel, 5.1 per centmolybdenum, .37 percent manganese and the remainder iron, which had amodulus of elasticity which changed only .15 per cent over the range of50 C. to 150 C., was produced'bysubjectinga body of the alloy to a coldarea reduction of 56 per cent and then annealing it at 400 C. Aternary"alloyof'40.1 per cent nickel, 10.8 per cent molybdenum, .17 percent manganese and the remainder iron, having a modulus of elasticitychanging less than @025 per cent over the range of 50 C.- to 150 C.,wasproduced by subjecting. a body of'the'alloy to cold area reduction of5 per cent and then annealing at 400 C. An alloy of 38.4 per centnickel, 10.7 per cent molybdenum, .13 per cent manganese and theremainder iron, having a modulus of elasticity changing less than .15per cent over the range of 50 C. to 150 C., was produced by subjectin abody of the alloy to a cold area reduction of anywhere between 41 percent and 67 per cent and then annealing at 400 C.

The invention has been described above as particularly applied toVibrating reed selector switches. It is apparent that the advantages ofof the invention can be employed in any device containing an elementwhich functions through elastic distortion, as for instance in devicesembodying a vibratory element such as a vibrating reed or a tuning fork.The invention will also be of value for use in devices utilizing springsfor measuring or applying force or for other purposes, such as balancesprings in clocks and watches. The invention has been described in termsof its specific embodiments and, since certain modifications andequivalents may be apparent to those skilled in the art, theseembodiments are intended to be illustrative of and not necessarily toconstitute a limitation upon the scope of the invention.

What is claimed is:

1. A metal element which functions through elastic distortion comprisinga body of an alloy annealed, at a temperature above 150 C. and below thetemperature of full recrystallization of the alloy, from a cold workedstate produced by subjecting said body to a cold area reduction of atleast 3 per cent, said alloy consisting of a composition defined withinthe area of an ironnickel-molybdenum ternary diagram bounded by thequadrangle having as its corners the four points defined by (1) 41.5 percent nickel and 58.5 per cent iron; (2) 37 per cent nickel, 11 per centmolybdenum and 52 per cent iron; (3) 42.5 per cent nickel, 12 per centmolybdenum and 45.5 per cent iron; and (4) 44.5 per cent nickel and 55.5per cent iron; and, in addition to said composition, up to .25 per centcarbon, up to 2 per cent manganese, up to 6 per cent aluminum, and up to5 per cent silicon, together with incidental impurities.

zltan' element as defined in claim 1; wherein the cold workedstate isthat produced by a cold area reduction of about 78 per cent, theannealing is at about 400 C., and the alloy consists of about 43' percent nickel, 0.66 per cent manganese and'i'the remainder iron togetherwith incidental impurities.

v:"3ifiA mechanicalvibratory' element in which thech'arge'in naturalfrequency over the temperature range'of 50 C. to C. is small, saidelement comprising a' body of an alloy annealed, at a temperature above150 C. and below' the temperatureor'fun recrystallization of the alloy,from acold" worked state produced by subjecting s'aid'lb'odyto a coldarea reduction of at least- 3 percent; said alloy consistin of acomposition defined Within the'area of an iron-nickel-molybdenum'ternary diagram bounded by the quadrangl'having" a's'its corners thefourpointsdefinedby. (l) 41 per cent nickel, 2 per centmolybdenum and 57percent iron; (2) 37 per cent nickel; -11, per cent molybdenum and 52per cent iron;', (3) 42.5 per cent: nickel, 12 per cent molybdenum and45.5- per cent iron; and (4) 44 per cent'nickel, 2per cent molybdenumand'54 per centiron; and,.in addition to said composition, up to 2 percent manganese, up to 0.25 per cent carbon, up to 6 per cent aluminum,and up to 5 per cent silicon, together with incidental impurities.

4, An element as described in claim 3 wherein the annealing temperatureis between 200 C. and 750 C. and the iron, nickel and molybdenum in thealloy are in the proportions of about 43 per cent nickel, 5 per centmolybdenum and 52 per cent iron.

5. A body, which exhibits only a small change in modulus of elasticityover the temperature range of 50 C. to 150 0., formed of an alloyannealed, at a temperature above 150 C. and below the temperature offull recrystallization of the alloy, from a cold worked state producedby subjecting a body of said alloy to a cold area reduction of at least3 per cent, said alloy consisting of a composition defined within thearea of an iron-nickel-molybdenum ternary diagram bounded by thequadrangle having as its corners the four points defined by 1) 41 percent nickel, 2 per cent molybdenum and 57 per cent iron; (2) 37 per centnickel, 11 per cent molybdenum and 52 per cent iron; (3) 42.5 per centnickel, 12 per cent molybdenum and 45.5 per cent iron; and (4) 44 percent nickel, 2 per cent molybdenum and 54 per cent iron; and, inaddition to said composition, up to 2 per cent manganese, up to 0.25 percent carbon, up to 6 per cent aluminum and up to 5 per cent silicon,together with incidental impurities.

6. A body as described in claim 5 wherein the cold area reduction isabout 56 per cent, the annealing temperature is between about 400 C. and600 C., and the alloy consists of about 41 per cent nickel, 5.1 per centmolybdenum, 0.37 per cent manganese and the remainder iron together withincidental impurities.

7. A body as described in claim 5 wherein the cold area reduction isabout 5 per cent, the annealing temperature is about 400 C., and thealloy consists of about 40 per cent nickel, 10.8 per cent molybdenum,0.17 per cent manganese and the remainder iron together with incidentalimpurities.

8. A body as described in claim 5 wherein the cold area reduction isbetween 41 per cent and 67 per cent, the annealing temperature is about400 C. and the alloy consists of about 38 per cent cent nickel, 10.7 percent molybdenum, 0.13 per cent manganese and the remainder iron togetherwith incidental impurities.

9. The method of reducing the amount by which the modulus of elasticityof a metal body varies with temperature over the range of -50 C. to 150C., which comprises subjecting to a cold area reduction of at least 3per cent, a. body of an alloy consisting of a composition defined withinthe area of an iron-nickel-molybdenum ternary diagram bounded by thequadrangle having as its corners the four points defined by (1) 41 percent nickel, 2 per cent molybdenum and 57 per cent iron; (2) 37 per centnickel, 11 per cent molybdenum and 52 per cent iron; (3) 42.5 per centnickel, 12 per cent molybdenum and 45.5 per cent iron; and (4) 44 percent nickel, 2 per cent molybdenum and 54 per cent iron; and, inaddition to said composition, up to 2 per cent manganese, up to 0.25 percent carbon, up to 6 per cent aluminum and up to per cent silicon,together with incidental impurities, and annealing said body at atemperature above 150 C. and below the recrystallization temperature ofthe alloy.

10. The method described in claim 9 wherein 8 the annealing is carriedout between 200 C. and 750 C.

11. The method described in claim 9 wherein thg annealing is carried outbetween 300 C. and C.

12. An element as described in claim 3 wherein the composition containsbetween 38.5 per cent nickel and 43 per cent nickel and between 4.5 percent molybdenum and 9.5 per cent molybdenum, and wherein the annealingtemperature is between 200 C. and 750 C.

13. An element as described in claim 3 wherein the composition containsbetween 40.5 per cent nickel and 43 per cent nickel and between 4.5 percent molybdenum and 8 per cent molybdenum, and wherein the annealingtemperature is between 300 C. and 600 C.

MORRIS E. FINE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,471,594 Weightman May 31, 19492,502,339 Perreault Mar. 28, 1950

1. A METAL ELEMENT WHICH FUNCTIONS THROUGH ELASTIC DISTORTION COMPRISINGA BODY OF AN ALLOY ANNEALED, AT A TEMPERATURE ABOVE 150* C. AND BELOWTHE TEMPERATURE OF FULL RECRYSTALLIZATION OF THE ALLOY, FROM A COLDWORKED STATE PRODUCED BY SUBJECTING SAID BODY TO A COLD AREA REDUCTIONOF AT LEAST 3 PER CENT, SAID ALLOY CONSISTING OF A COMPOSITION DEFINEDWITHIN THE AREA OF AN IRONNICKEL-MOLYBDENUM TERNARY DIAGRAM BONDED BYTHE QUADRANGLE HAVING AS ITS CORNERS THE FOUR POINTS DEFINED BY (1) 41.5PER CENT NICKEL AND 58.5 PER CENT IRON; (2) 37 PER CENT NICKEL, 11 PERCENT MOLYBDENUM AND 52 PER CENT IRON; (3) 42.5 PER CENT NICKEL, 12 PERCENT MOLYBDENUM AND 45.5 PER CENT IRON; AND (4) 44.5 PER CENT NICKEL AND55.5 PER CENT IRON; AND , IN ADDITION TO SAID COMPOSITION , UP TO .25PER CENT CARBON, UP TO 2 PER CENT MANGANESE, UP TO 6 PER CENT ALUMINUM,AND UP TO 5 PER CENT SILICON, TOGETHER WITH INCIDENTAL IMPURITIES.